Low-income children are significantly more likely to be obese, experience chronic stress, and have difficulty self-regulating their emotions and behavior in response to stress. Socioeconomic disparities in obesity begin in early childhood and track throughout the lifespan, but the etiology of such differences is unclear. One way that stress is hypothesized to "get under the skin" is via changes in the hypothalamic-pituitary-adrenal (HPA), or "stress" axis and patterns of cortisol secretion. Under conditions of chronic stress, such as poverty, aberrations in both the normal diurnal pattern of cortisol secretion and cortisol reactivity to stress occur. Obese, compared to non-obese, adults often show such aberrations. Young children living in poverty can also often demonstrate aberrant patterns of cortisol secretion in response to stress;yet, no study has examined links between stress, cortisol, self-regulation, and obesity in low-income children. Studying how the cycle of poverty, stress, and obesity begins early in life is vital, because once established, obesity typically persists. We propose to build on our existing Challenge Grant parent study of diurnal cortisol patterns, eating behavior and obesity in Head Start children (NIH 1RC1DK086376-01, Cortisol and Eating Behavior in Low-Income Preschool-Aged Children, Principal Investigator Lumeng) to investigate associations between poor emotional and behavioral self-regulation and increased obesity risk. We will specifically examine aberrant patterns of cortisol reactivity to stress as a mediator of such associations in this unique cohort of young, low-income children. We are an interdisciplinary team that studies biologic, psychological, and behavioral processes in order to examine the complex relationships among stress, cortisol, self-regulation, and obesity. Improved understanding of associations between self-regulation and obesity in low-income preschool-aged children will provide new points for targeted obesity prevention and intervention programs for young children that focus on self-regulatory skills. Structural equation modeling will be used to examine potential associations. Specific aims are, among 250 low-income 3- to 5-year old children: Aim 1: Examine the association between self-regulation and child body mass index (BMI) z-score. Aim 2: Examine the association between patterns of cortisol reactivity to stress and child BMI z-score. Aim 3: Examine cortisol stress reactivity patterns as a mediator of the association between self-regulation and child BMI z-score. Aim 4: Examine change in BMI z-score (over 18 months) in relation to these variables, and to predictors from our Challenge Grant parent study (e.g., diurnal salivary cortisol pattern, comfort food intake, emotional eating). Study results will have implications for understanding mechanisms of self-regulation, stress, cortisol, and obesity in young children in relation to the early emergence of health disparities. PUBLIC HEALTH RELEVANCE: Socioeconomic disparities in obesity begin in early childhood and track throughout the lifespan, but the etiology of such differences is unclear. Aberrations in the hypothalamic-pituitary-adrenal (HPA), or "stress" axis, and cortisol production in response to stress is suggested as one way for stress to "get under the skin" and lead to adverse health outcomes such as obesity in chronically stressed, impoverished populations. Altered cortisol patterns are also seen in children with emotional and behavioral self-regulation difficulties. We will examine associations between poor self-regulation and increased obesity risk, and test whether cortisol reactivity to stress mediates such associations, in a sample of 250 low-income preschool-aged children. Results have implications for understanding mechanisms of self-regulation, stress, and obesity in young children, and how early health disparities may arise.